Risk of endometrial cancer in relation to use of low-dose, unopposed estrogens.
OBJECTIVE
To determine whether a low dosage (0.3 mg/day) of unopposed conjugated estrogens can be used without incurring an elevated risk of endometrial cancer.


METHODS
In this case-control study, cases (n = 484) consisted of women diagnosed with endometrial cancer between 1985 and 1991 in three counties in Western Washington. Controls (n = 780) were identified using random digit dialing within the same three counties. Subjects were interviewed in person to obtain basic demographic and medical history information, as well as specific information about hormone use.


RESULTS
Eighteen cases and eight controls had taken 0.3 mg/day of unopposed conjugated estrogens and no other dose or preparation of estrogens (risk relative to that of women who had not taken postmenopausal hormones = 5.4, 95% confidence interval [CI] 2.3, 13.0). The risk was particularly high in women whose use of this dose was both current and of more than 8 years' duration (odds ratio = 9.2, 95% CI 2.9, 29.0). The elevation in risk in users of 0.3 mg/day was similar in size to that associated with the daily unopposed use of 0.625 mg of conjugated estrogens.


CONCLUSIONS
The results suggest that a dosage of 0.3 mg per day of unopposed conjugated estrogens is associated with an increased risk of endometrial cancer.
Cushing
K L
KL
Fred Hutchinson Cancer Research Center, and the Department of Epidemiology, University of Washington, Seattle 98109-1024, USA. kcushing@fhcrc.org
Weiss
N S
NS
Voigt
L F
LF
McKnight
B
B
Beresford
S A
SA
D000368:Aged; D016022:Case-Control Studies; D016001:Confidence Intervals; D016889:Endometrial Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D015914:Estrogen Replacement Therapy / Q000009:adverse effects* / Q000379:methods; D004966:Estrogens, Conjugated (USP) / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D012923:Social Class; D014861:Washington / Q000453:epidemiology
D004966:Estrogens, Conjugated (USP)